Draft control mechanism



Oct. 6, 1953 T. w. BoHMKER DRAFT CONTROL MECHANISM 3 Sheets-Sheet 2 Filed May 25, 1946 INVENTOR s w. BOHMKER ATTORNEYS THO A Oct. 6, 1953 T, w, BOHMKER 2,654,301

DRAFT CONTROL MECHANISM 3 Sheets-Shree?l I5 Filed May 23, 194e INVENTO T O AS W. BOHMK BY 7 l) /l'ff ATTORNEYS Patented Oct. 6, 1953 Thomas W.. Bohmken,

kGeneseo,` Ill., assigner to Deere-8a Gompany, Moline, Ill., a corporation olf-Illinois Application May 23;,1946, Serial No. 671,672, l'fclaims. (Cl. 957-46203) The present invention relates generally to control mechanism and more particularly to mechanismforV adjusting an agricultural implement,

such as. a ground working tool or the like, while.V

the latter is lcontrolled bya draft vehicle such as a tractor.

The principal object of the present invention is the provision of mechanism which will automatically adjust the implement to maintain the latter in proper operating position under varying draft conditions. More specifically it is a further object of my invention to provide control mechanism for raising and loweringV a working tool under varying ground conditions to preE vent overloading the tractor or vehicle while maintaining a maximum working effectiveness of the tool.

During operation of a tractor propelled tool, such as a plow or the like, the variation of ground conditions results in wide variations in the amount of draft force required to move the plow or other tool in the ground. For example, when the plow encounters dense or tightly packedV soil conditions, it requires more draft force to move it through the dense soil at any given depth of operation than when the plow is operated at the same depth of operation in light soil conditions.

Control mechanism is known in the art for bal-,-

ancing the draft force or tractive effort against a spring and then raising or lowering the plowshare or other ground working tool to maintain- Thus,

a substantially constant tractive effort. should the plow encounter an area of hard clay, the increased tractive eifort required effects a response from the mechanism, which raises the plow to a depth at which the tractor can pull the plow with the predetermined value of tractive effort. Then, when the plow passes from the clay to a lighter or sandier soil condition, the tractive effort decreases, causing a further response from the mechanism, which lowers the implement to a depth of operation at which it requires the Vpredetermined amount of tractive effort for its propulsion. This prevents the tractor from beingV overloaded in a manner similar to that used in manual operation. This type of mechanism however, does not solve the entire problem, for there are other factors besides the increasing of the draft force, which can result in the overloading of the tractor. For example, when plowing uphill, more power is required from the tractorengine to move the weight of the tractor itself] which reduces vthe amount of power available for propelling the plow. Conventional mechanisms Ado not take this factor into account, lbut maintain the same amount of' tractive effort whenk plowing uphill as when plowing on level ground,

Another condition which prior art systems do', not take into account islthat which occurs when the tractor encounters a slippery lspot lin'tlfle field, resulting in increased wheelslipping. When the tractor wheels begin 'tov slip, the tractive effort decreases which, in prior artsystems, causes the depth ofthe plow to bein'creased, rather Vthan decreased, and thus, the prior art systems failen'- tirely under such groundl conditions, making it necessary to revert to manual-operation in 'slippery ground conditions.

It is, therefore, one ofthe objects ofmy invention to provide control mechanism for raising and lowering a ground working tool responsive" to conditions that result in a decrease forward speed of the tractor, regardless of the cause of such conditions, whether it be from increased draft force required to ldraw the implement,` from increased power requirements to move the tractor, such as when plowing uphill, or fromv slippery ground conditions that prevent the exertion by the tractor of its normal draft force on the plow.

In the accomplishment of these objects, my invention contemplates the use of control mech'- anisrn responsive to changes in the anioulnt of Thus, by holding slippage of the tractor wheels. n l i Y 1 a substantially constant valuey of wheel slippage, or in other words, a constant difference between the speed of the tractor over the ground and the peripheral rspeed of the traction wheels, the tractor is prevented from overloading andstalling under any conditions of operation. Forexample, should the plow encounter a spot in which thesoil is'y dense, the increaseddrag on theimplement causes an increased wheel slippage, thereby resulting in a response from the mechanism which lifts the plow to a shallower operating depth until the 'slippage of the wheels is reduced to its predetermined value. when plowing uphill, the increased power requirement for propelling the tractor up the hill causes an increase in wheel slippage and thereby calls for decreasing the depth of operation of the plow. Likewise, when the tractor encounters a slippery area, the wheel slippage increases, thereby resulting in the plow being raised until the wheel slippage is reduced to normal.

In a simplified form, my invention contemplates automatic control mechanism for raising and lowering the tool, responsive to changes in the forward speed of the tractor over the ground, to hold a substantially constantv forward speed.

Similarly,

In this form of my invention, the implement is not raised to a shallower depth of operation so long as the speed of the tractor can be maintained at its normal value by the conventional tractor governor provided as standard equipment on most commercial tractors. Thus, the depth of operation of the plow or other tool is maintained constant until the forward speed of the tractor decreases, either by virtue of excessive wheel slipping or because of overloading of the tractor engine, either by increased draft due to dense soil conditions or by increased power requirement due to plowing uphill.

These and other objects and advantages of my invention will be apparent to those skilled in the art after a consideration of the following description, in which reference is had to the drawings appended hereto, in which art, provides for simultaneous operation of the two crank axles when raising and lowering the plow.

The plow 2l is raised and lowered between operating and transport positions by poweractuated tool shifting means in the form of a hydraulic cylinder 43, within which is slidably disposed a piston 44 having a connecting rod 45 extending out of one end of the cylinder 43 and connected to a bell crank 46 pivotally mounted at 41 on the plow frame and having a link connection 48 with one of the crank axles 3l. The plow is raised by extending the piston and cylinder assembly 43, 44, thereby swinging the crank axles downwardlyto raise the plow frame 2|. The depth of operation of the plowshares 29 can be controlled within a limited range of opera- Figure 1 is a top plan view of a tractor and plow embodying the principles of the present invention;

Figure 2 is a sectional elevational view taken through the axis of the differential gear mechanism;

Figure 3 is a perspective view or the control mechanism embodied in the present invention;

Figure 4 is a sectional elevational view taken along the axis of the hydraulic control valve;

VFigure 5 is a perspective view of a modiiied form of the control mechanism;

Figure 6 is a sectional elevational view of either of the two overrunning clutch devices in Figure 5, as indicated by lines 6-6 in Figure 5; and

Figure 7 is a View similar to a portion of Figure 2 but showing a further modication of the invention.

Referring now to the drawings, the tractor is indicated in its entirety by reference numeral I and comprises a narrow longitudinally extending body II carried on a transverse rear axle housing I2, which is supported on drive axles I3, I4, to which are attached traction wheels I5, I6, respectively. The forward end of the body II is carried on a pair of closely spaced front dirigible wheels I1 in a manner well known to those skilled in the art. Power is transmitted from the engine of the tractor located on the body I I to the two traction wheels I5, I by means y of a longitudinally extending power shaft I8 which is connected to the two axles I3, i4 by conventional differential gear mechanism located in the transverse housing I2. The tractor is provided with a conventional drawbar 2U, to which is connected a trailing implement, shown as a plow 2 I.

The plow 2I comprises three laterally spaced fore and aft extending beams 22, 23, 24 interconnected at their forward ends by a transverse beam 25, to which is connected a forwardly extending draft member 26. The draft member 2B is pivotally connected to the drawbar by a hitch pin 21. The draft beams 22, 23, 24 are rigidly interconnected by suitable braces 28, which tie the draft beams together to form a rigid unitary frame. Each of the beams 22, 23, 24 carries a plowshare usual manner.

The plow 2I is carried on a pair of transversely extending crank axles 3l, 32, which are `ournaled on the plow frame and are carried lon wheels 33, 34, respectively. The crank axles 3|, 32 are interconnected by means of a link 45, which is pivotally connected to lever arms 4I, 42 fixed to the axles 3l, 32, respectively. This interconnection, as is well known to those skilled in the 29 at its rear end, in the tion by means of the hydraulic cylinder.

The hydraulic cylinder 43 is controlled by mechanism which will be described later, contained within a control housing 50 mounted on the tractor, and is connected by means of a pair of exible hoses 5I, 52 to the control mechanism. The hoses 5I, 52 are connected to the cylinder 43 at the front and rear ends thereof, respectively, for supplying fluid under pressure to the cylinder on either side of the piston 44, selectively, to raise and lower the plowshares during operation and also to raise the plow from operating position to transport position in a conventional manner.

Fluid is supplied to the cylinder 43 through the hoses 5l, 52 under control of a hydraulic control valve 53, which comprises a valve housing 54, within which is a cylindrical valve chamber 55, best shown in Figure 4. A valve member 56 is slidable axially within the chamber 55 and is provided with an actuating rod 51 extending outwardly of the casing 54 through an opening 58 in one end of the latter.

Fluid is supplied to the valve chamber 55 through a conduit E0, which is connected to any suitable source of fluid such as a fluid pump (not shown). 'I'he supply duct Gil is connected to a supply port 6I in the valve housing 54, substantially centrally located in the valve chamber 55. A pair of exhaust ports B2, 63 are connected through ducts 64, 65, respectively, with a fluid reservoir (not shown). The exhaust ports 62, 63 are spaced axially on opposite sides of the supply port 5i, respectively. A pair of cylinder ports 66, 61 are disposed in communication with the valve chamber 55 on opposite sides, respectively, of the supply port 6I, between the latter and the adjacent exhaust ports 52, G3, respectively. The cylinder ports B6, 61 communicate with a pair of check valve chambers 58, 69, within which are disposed poppet type check valves 10, 1 I, which normally block the passage between the associated cylinder port and the check valve chamber. A pair of compression springs 12, 13 are disposed in the check valve chambers 68, 69 and urge the check valves 1U, 1I into closed position, respectively, to prevent fluid from flowing from either end of the cylinder 43 to the valve chamber 55. The check valves 1B, 1I are provided with valve stems 16, 11, which extend through suitable apertures to the valve chamber 55, the valve stems 16, 11 bearing against outwardly tapering conical surfaces 18, 19 on the valve member 56, respectively. Thus, by shifting the actuating rod 51 the valve member 56 can be shifted axially within the cylinder 55 in two relatively opposite directions from the neutral position indicated in Figure 4, to open one or the otherk of the check valves 10, 1| by a camming action of the conical surface 18, 19 against the valvestems 16, '11, selectively.

` In the neutral position of the valve member 56. the fluid is supplied through the conduit and supply port 51| to the valve chamber 55 and is free to now in both .directions simultaneously `to the two exhaust ports 52, 63, returning `to the fluid reservoir through the exhaust ducts '64, 65. The valve member '55 is 'provided with a central portion 80, which is slidable within the valve chamber 55, but is narrower than the supply port 5|, to permit a flow of the supply fluid in each direction in the chamber 5.5. A pair of pistons 3|, 82 are also provided on the valve member 5.6 in outwardly spaced relation from the central portion on opposite sides `of the latter, respectively. The two pistons 81|, 82 are disposed in spaced relation from the central portion y8:0 so that, in neutral position, the exhaust ports 62, 63 are uncovered, whereby the now of fluid returns' to the reservoir through the `exhaust .ducts 6-4, 65.

The operation of the valve 53 is as follows: By shifting the actuating rod :51 outwardly, or toward the right, as viewed in Figure 4, the piston portion 80 'blocks the flow of uid from .the supplyport -61 toward the exhaust port 63, and at the same time, the piston portion 8| blocks any flow of uid from the valve chamber 55 to the exhaust port 62. The fluid supply from the port 6| forces the check valve 10 open against the spring 12 and .passes through the flexible hose 52 to the'cylinder 43, building up the pressure on one side of the piston '44 and urging the latter rearwardly, as'viewed in Figure 1, thereby raising lthe plow by forcing the wheels downwardly relative to the plow beams. The fluid in the cylinder 43' on the opposite side of the piston is forced outwardly through the other hose 5| past f the check vvalve 1|, which has `been forced open by the camming action of the conical surface 19 against the end of the valve stem 11.V The fluid then ows through the cylinder port v|11 out the exhaust port 03, and then returns to the reservoir through the duct 65.

Whenever the valve member 56 is returned to neutral position, the flow of fluid from the supply port 6| to the exhaust ports 52, 53 is reestablished. and the check valves 10, 1| are closed by the action of the springs 1.2, 13, thereby holding the plow -in any desired position .of adjustment.

The plo-w can be lowered by shifting the valve member 55 inwardly or to the left (see Figure 4)., thereby blocking the -iiow of fluid from the supply port 6| through the valve chamber 55 toward the exhaust port 62. The fluid is thus directed from the supply port 5| to the cylinder por-t 51. The piston portion 82 blocks the exhaust port 63, thereby preventing any-escape of fluid, whereupon pressure builds up in the cylinder port .61, opening the check valve 1|. The fluid then news through the flexible hose 5| to the rear end of the cylinder, as viewed'in Figure 1, acting to force the piston 44 forwardly in the cylinder 43, thereby lowering the plow. The fluid from the forward end of the cylinder 43 nows outwardly through the hose 52 and past the check valve 10, which has been forced open by a camming .action of the conical portion 18 :against the valve stem 16. The fluid flows through Ithe lcylinder port ES into the valve chamber 55 and out through the exhaust port .52, returning to the reservoir through the duct 164. The lowering movement can be interrupted at any desired polntfby ing the valve member 56 back to neutral: position@ The amount vof slip of the trac-tor wheelsnl5,v i5.

pair of cooperative flanged housing sections 81 88 connected together by bolts 85 to the housing anges. Each of the housing sections 8-1, 88. is provided with a bearing hub 90', 90, the hubs being adapted to receive a pair of trunnions 91|, 92, respectively, of a differential cage member 93. The cage member 93 carries a pair of pinions 9.4, 95 therein, the pinions being journaled on a shaft 96, which extends diametrically through the cage 93 and is supported at opposite ends thereof, respectively, in the walls of the cage. The trunnions 9|, 92 are provi-ded with axially spaced openings to receive a pair of movable elements, here--A in drive shafts |00, |0| journaled therein. On the inner ends of the drive shafts |00, |0.| are fixed a pair of differential gears |02, |03, disposed in mesh with the two pinions 54., .95.

As is well known to those skilled in the art., when the shaft |00 is turned in one direction of rotation at a given speed and the other drive shaft |.0| is turned in the vopposite .direction at..

the same speed, the pinions 90,Y 95 .are -driven in relatively opposite directions, but the .cage 9,3 re.- rnains stationary. When the shaft |00 is driven at a greater speed of rotation than the other shaft |0|, however, the cage 93 is rotated in one direction at a speed which is one-half the `dif--Y ference between the speeds of the two shafts |00., |0I. Conversely, when the shaft `|00 turns .at ka slower speed than the :other shaft |01, the cage 93 rotates in the opposite direction at a .speed equal to half the-difference between the ^speed of the shafts |00, |0|.

The cage 93 is provided with a ring gear |04 extending lperipherally around the. outside of thecage 53 and disposed in mesh with a comparatively small pinion |D5 mounted rigidly on ashaft |05. The pinion |05 is disposed within a recess |01 in one of the housing sections v8.8 and the shaft |06 is journaled in the 'housing section Ion` opposite sides of the recess |01 and extends outwardly of the differential housing,y

The differential shaft |00y is rotated in the direction of the arrow A (Figs. 1 and '2) nat .a speed proportional to the speed of forward travel of the tractor by means which will be described, while the other differential shaft |0| is driven at a speed proportional to the peripheral speed of the traction wheels I5, I6 inthe other direction of rotation (arrow B, Figs. 1 and 2), with the result 'that the speed of the shaft |06 is an indication of the difference between the peripheral' speed of the wheels 5, IB .and the forward speed of the implement, or in other words, the amount of slip of the tractor wheels I5, 6.

The forward speed of travel of the tractor is measured by means of a rotary motion-transmitting element or device, here `a ground engaging wheel ||0 xed to an axle journaled in abearing ||y2 on a crank arm H3 swingably mounted in a bearing |14 on the tractor body The crank arm H3 -is free to swing in a vertical plane about the axis of thesupporting bearing |-|4 to permit the wheel ||0 to roll over the ground and to maintain contact therewith. The inner end rof the axle y| has a lbevel zgear `l .1| y5 in .mesh

l with a bevel gear H6. The gear ||6 is connected through a exible sheathed power transmitting cable drive |20 to drive a conical pulley |2| of an adjustable speed device |22. The other conical pulley |23 of the adjustable speed device |22 is connected to drive the shaft |00. The two conical pulleys |2I, |23 face in relatively opposite directions and are interconnected by a power transmitting belt |24. The speed of the shaft can be adjusted relative to the speed of the wheel |0 by shifting the flexible belt |24 axially of the conical pulleys I2 |23, as is well known to those skilled in the art. The mechanism for transmitting rotary motion from the ground wheel ||0 to the shaft |00 with provision for adjusting the speed of the shaft |00 relative to the speed of the wheel I|0 is not set forth in detail, for any suitable mechanism known to those skilled in the art can be used for this purpose.

In any event, the drive mechanism ||5, H6, cable |20, pulleys |2|, |23 and belt |24 connect the wheel and shaft |00 and the latter thus is means for indicating the forward speed of the vehicle over the ground.

The other differential shaft |0| is connected through a sheathed fiexible power transmitting cable drive to a bevel gear |0| in mesh with a bevel drive gear |32 mounted on the tractor power shaft |8. I nasmuch as the two tractor axles I3, |4 are driven through differential gear mechanism in a conventional manner, the peripheral speeds of the two wheels l5, |6 are not necessarily equal, such as when making a turn, but the speed of the drive shaft I8 is proportional to the average of the peripheral speeds of the two wheels l5, I6. Thus, the shaft l0 is a movable (here rotary) motion-transmitting device or element that moves (or rotates) at a speed proportional to the peripheral speed of the traction wheel means, and the shaft |0| is means for indicating the peripheral speed of the traction wheel means.

If the speed of one of the differential shafts |00 were to be made directly proportional to the peripheral speed of the ground wheel ||0 in exactly the same ratio that the other differential shaft |0I is proportional to the average peripheral speed of the two traction wheels |5, I6, the rotary indicating shaft |06 would stand statione ary only when there is no slip of the traction wheels I5, I6 during operation. In such case, the speed of rotation of the indicating shaft |06 would then be directly proportional to the amount of slip of the tractor wheels when the tractor is operating under load. For the purposes of the present invention, however, it is desirable to so construct and arrange the mechanism that the indicating shaft |06 is stationary when the tractor wheels |5, |6 are slipping at a normal predetermined value. This can be adjusted by shifting the belt |24 on the adjustable speed device |22 to bring the speed of rotation of the differential shaft |00 and gear |02 to a value equal to the speed of the differential shaft |0| and gear |03 under the desired load and ground conditions under which the tractor is to be operated.

Thus it will be evident that if the adjustable speed device |22 is adjusted to bring the indicating shaft |06 to a stationary condition while the tractor is being driven forwardly with the plow in operating position at the proper depth, then should the draft of the plow increase or the tractor wheels encounter a slippery spot in the field, the slip of the tractor wheels |5, I6 will increase, causing the indicating shaft |06 to begin to rotate in the direction of the arrow AC (Figs.

2, 3, 5 and 6). Conversely, should the plow en` counter lightersoil conditions, the draft force will decrease, resulting in less slip of the tractor wheels I5, |6, whereupon the indicating shaft |00 will begin to rotate in the opposite direction (arrow D, Figs. 2, 3, 5 and 6).

The rotary indicating shaft |06 extends into the control housing 50 and is supported in a pair of spaced bearings |35, |36 carried on a pair of brackets |31, |38, the latter being secured to the wall of the housing. A spur gear |30 is rigidly mounted on the indicating shaft |06 between the two bearings |35, |36 and is in mesh with a smaller spur gear |40 fixed to a countershaft |4I. The countershaft I4| is journaled in a pair of bearings |42, |43, which are carried on a pair of brackets |44, |45, respectively, secured to the wall of the housing 50. The indicating shaft |06 is disposed in alignment with an actuating shaft |50, carried in a bearing |5| mounted on a bracket |52 which is supported on the wall of the housing 50. The actuating shaft carries an actuating arm |53 rigidly secured thereto. The

actuating arm |53 extends upwardly and is biV furcated to straddle the actuating rod 51 of the valve member 56. The ends of the arm |53`are provided with vertical slots |54, which are connected to the rod 51 by a pin |55 which extends through the slots |54 and through an aperture |55 in the rod 51. Thus, it is evident that angular movement of the actuating shaft |50 about its axis in relatively opposite directions will act through the arm |53 to shift the valve member 50 in either direction within the valve chamber 55 from the neutral position of the valve member, as shown in Figure 4. A pair of opposed coil springs |56a are connected at their inner ends to the actuating arm |53 and at their outer ends to brackets |51 secured to one of the walls of the housing 50. Hence, the springs |56a tend to center the valve member 56 in its neutral position.

The actuating shaft |50 is provided with a friction clutch disk |50 mounted rigidly on the inner end of the shaft |50 in operative relation to a friction clutch disk IGI which is mounted on a hub |62 slidable axially on the indicating shaft |06 but prevented from rotating on the shaft |06 by a suitable splined connection |63. The hub |62 is grooved peripherally at |64 to receive a shifting fork |65, which is pivotally mounted on a supporting pin |66 carried on a bracket |61, which is fixed to one of the housing walls. The upper end of the shifting fork is also bifurcated at |68 to engage a peripheral groove |69 in a sleeve |10 which is slidable axially along the countershaft IM. The sleeve |10 forms a part of a speed responsive device or mechanism such as a governor |1| of the flyball type, which also includes a sleeve or hub |12 fixed to the shaft |4| and connected to the slidable sleeve |10 by two pairs of toggle links |13, which are provided with flyballs or weights |14 at their intermediate joints, following conventional construction. A coil spring |15 encircles the countershaft |4| between the hub |12 and the sleeve |10, tending to force them apart and to swing the shifting fork |65 in a clockwise direction about its pivot pin |66, and thereby separating the clutch plates |60, |6|.

When the countershaft |4| is rotated in either direction, the lyballs |10 are thrown outwardly by centrifugal force and compress the spring |15 by pulling the sleeve |10 toward the hub |12,

'thereby swinging the shifting fork |65 in acountercloelcwise direction (to the left in Fig. 3) to engage the friction disks I 60, |-6I. The clutch disks thus transmit rotary motion from the indicating shaft |06 to the actuating shaft |50',

thereby swinging the actuating arm |53?` in one direction or the other, depending upon the direction of rotation of the indicating shaft E06.

V`With the indicating' shaft I 06 stationary,- the countershaft I`4I is also stationary' since it is geared thereto by the gears |39,V I 40.A The spring |115 urges the sleeve |10 away` from the hub Il'H, thereby separating the clutch disksIBIJ', IGI, and permitting the centering springs |56a to hold the valve member 56 in the neutral position. Both of the check valves T0, 'II are closedand thereforeI the piston 4'4 is locked against movement in either direction in the cylinder 43:, thereby holding th'e plow at its given depth ot operation. Any' change in the ground conditions which tend tol overload the tractor', such as an increase in density in the land being! plowed, an upward slope to the ground, or slippery ground conditions, all tend to cause the forward speed: of the tractor to decrease, or the speed ofr theA tractor wheels |-5, |6 to increase, or both. In any case, the speed of the movable element or differential shaft decreases relative to the speed of the difierential shaft I0|,. thereby'causing the differential cage 03 to rotate in the direction of the arrowV E (Fig. l2), thereby causing the indicating shaft |06 to be driven'- through the-gears |104',Y |05 in the direction of the'- arrow Cl (Figs. 2,. 3,. 5 and 61)'. The gear ratio issuch that the indicatingy shaft |06 rotates atn a` higher speed than thecagef 93, which drives the coun-tershaft |'4'I' at azstillhigher speed.V When the speed; of the fl'yball governor IAII overcomes the pressure of the spring M5, the clutch plate |6| is shifted linto contact,- with the clutch plate i60, and since the shaftl is turning in` its` clockwise.' direction,1 as .viewed in Figure 3 (arrow (-1)" the: motion is transmitted throughthe clutchv plates: to the actuating shaft I50,.which1 swings the actuating. arm: |53; to. shi-ft the valve` member 56.- in its raise direction, or to; the right, asivi-ewed in Figures 3f and: 4.1 This directs fluidi under pressure through the hose 52 toIk the forward end of the cylinder 4,3- and eX- tends the piston rod 45- thereby forcing the wheels 33, 34 downwardly and raising theypiowshares 29. Decreasing the ,depth` of operation Aof) the plowshares has theeiect ofv relieving the-load on the tractor, permitting the. latter tok increase Vits forward speed and to decreasethe amount of slip of the tractor wheels |5, I6. This causes the indicating shaft |06V to slow dow-n' to a point at which the spring I` willV overcome the. centrifugal force of the yballs |'|.4` and separate the clutch plates |60, |61, therebypermittingthe springs |56@ to center the actuating" arm |53 and the valve member 56 in neutral position. The slip of the tractor wheels |551 '|61 has now been Brought back to the Vnormali- -va1ue,= whichJ was determined by the setting of the adjustable speed device |22 when the implement was operating under the assumed average operating conditions. Thus, the Valve means 53 and mechanism. of

Fig.- 8 comprise means responsive to variations in the speed of the element for controlling the shifting means or' cylinder and piston. assern bly is, t4- to selectively increase or' decrease the the'A working tool, Stated otherwise, this means reects variations in theA speed of forward travel of the' implement for controlling the working depth of the plow bottom. 'I'hevalve meoh'aism ofv Fig. 4 is' representative of one from ofmeans respons'ive' to the reflecting means for control'- ling the tool-shifting' means 43-4'4'.

After the overload conditions have been r'emoved, such as, for example, by the plow encountering lighter soil or by the tractor wheels leaving the slippery ground surface and obtaining bettertraction once more, then the anm'unt of wheel slipping will be decreased below its normal value, in View of the lighter' load on the tractor occasioned by the plow operating at reduced depths. In other words, the forward speed of the tractor would be increased relative to the speed of the wheels and the' speed of the' shaft |001 would exceed that of theshaft |0I?, thereby causing the shaft |06 to begin to rotatevv in the direction of the arrow D, as viewed-in Figures 2, 3', 5 and 6. The rotation of! the counter shaft IM will again cause the shifting fork |65? to engage the clutch disks i60, IlB-|-. The' D rotation of the shaft |06 is transmitted through the clutch to swing the actuating shaft and arm |53 in a counterelockwise direction (as seen in Fig. 3)', thereby shifting the valve meinber'5`6 toward the left, as viewed in- Figures 3 and 4, directing hydraulic fluid under pressurev through the' hose 5| to retract the'v piston rod t5 for lower' ingv the plow into the'g'round. This results in an increased drag on the tractor so that the slip increases again tol itsnormal value, causing; the indicating shaft |`06fto1be brought to a standstill, thereby separating the clutch disks |160, IJIrI, and permitting the springs |56@ toI again'- c'eriter the valvejm'ember 56 in neutral position;

It is to' be noted' that although a change o'f wheel slippage results in a' continuous rotation of the indicating shaft P06-'in one directionI (under one condition or the other), the actuating shaft |50v and actuating arm |53v can' rotate through only a comparatively' small angle until' the" valve member 56` reaches the end of its' range of. shiftingmovement within-the-valve casing 54. Fur#- ther rotation of the indicating shaft |0`6f` is" ac comlnodatedV by the clutch plate' I6'I' slipping relative'to the clutch plate |60, the latter'reniairi` ing stationary untilVv the speedv ofr rotation of' e indicating shaft |06 decreasesto the point wherthegovernor mechanism separates the plates IGI), Nil, whereby the 'centering springs |5I5a are permitted to return the valve member 5`6 to neutral position.

Referring now more particularly toA Figures 5 and 6, the modif-lodi form of the present inven'e tion-'includes the rotary indicating shait Il06 which`v is supported in a4 pair of laterally spaced journal bearings |00, ISI;` which@ are mounted on` a pair of supporting'bracketsl H32,- |83, respectively,v carried by a. wall of the control. housing 50. In this embodiment the actuating ar-m |84; to which thev actuating rod 57|- of the vali/remember 56: is. connected, is pivotall-y` mounted on a bollt |851whichlissupportedona boss lfext'endw ing outwardly from the wall of the housing 50;

il The lower end of the actuating arm |84 is provided with a transversely extended portion |81 in which is provided a plurality of laterally spaced apertures |88 to receive the pivot bolt |85. The

i actuating arm |84 and the valve member 56 are centered in neutral position by means of a pair of centering springs |89 connected in opposed relation to the arm |84 and anchored to a pair of brackets |90 on opposite sides of the arm, respectively. The upper end of the actuating arm |84 is provided with a U-shaped shifting member |95, having two upwardly extending legs which engage a pair of grooves |96, |91 in a pair of sleeves |98, |99, respectively. The sleeves |98, |99 are loosely and slidably mounted on the indicating shaft |06 and are also rotatable relative thereto and to each other. The sleeves |98, |99 are part of a pair of speed responsive devices 200, 20|, respectively. Each of the devices 200, 20| also includes a second sleeve or hub member 202, 203, respectively, which is journaled on the shaft |06 but secured by a collar 204 to prevent axial shifting movement of the sleeves 202, 203. Each of the journaled sleeves 202, 203 is connected with its associated slotted sleeve |98, |99 by means of a plurality of pairs of toggle links 205 having weights or flyballs 206 connected to the intermediate joints between the links. Thus, it is evident that rotation of each of the speed responsive devices 200, 20| causes the iiyballs 206 to move outwardly from the axis of the shaft |06 by centrifugal force, thereby tending to shift the sleeves |98, |99 away from each other toward the journaled sleeves 202, 203.

The drive means for the two speed responsive devices 200, 20|, however, is so arranged that the speed responsive device 200 is rotated when the shaft |06 rotates in the direction of the arrow C (Figs. 2, 3, and 6) and the other speed responsive device is rotated when the shaft |06 rotates in the other direction (arrow D). This is accomplished by means of a pair of one way or overrunning clutches connected between the shaft |06 and the sleeves 202, 203 for driving the latter by rotation of the shaft |06 in opposite directions, respectively. Each of the speed responsive devices 200 and 20| is provided with a fixed hub 201, 208, which is rigidly fixed to the shaft |06 and is provided with a neck portion 209 of reduced diameter, which extends into a recess 2 |0 in the outer end of the sleeve 202, 203, best shown in Figure 6. The neck portion 209 is of appreciably smaller diameter than the recess 2|0 to provide a space therebetween to receive three rollers 2|| disposed generally parallel to the axis of the shaftA |06. The inner surface of the recess 2 |0 is provided with three clutch surfaces 2|2 which curve inwardly in converging relation to the outer surface of the reduced portoin or neck 209, between which converging surfaces the rollers 2|| become wedged when the shaft |06 rotates in one direction of rotation. As viewed in Figure 6, when the shaft |06 and neck portion 209 rotate in a counterclockwise directionV (arrow D), the rollers 2|| are urged into wedging relation between the cylindrical surface of the neck portion 209 and the converging surface 2|2 to drive the hub 202 in a counterclockwise direction. However, when the shaft |06 and neck 209 are rotated in a clockwise direction (arrow C), the rollers 2|| are urged out of wedging engagement into the enlarged space between the portion 209 and the hub 202, with the result that the latter is not rotated with the shaft.

It will be noted that Figure 6 represents secu tions taken along either of two lines 6-6 in Figure 5, looking in opposite directions relative to the shaft |06 and therefore it is evident that when the shaft rotates in a clockwise direction, arrow C, as viewed in Figure 5, as a result of decrease in ground speed of the tractor, the speed responsive device 200 is rotated with the shaft |06, While the other speed responsive device 20| is disconnected from the shaft |06 and therefore stands stationary. lRotation of the device 200 with the shaft |06 causes the flyballs 206 to be urged outwardly, thereby drawing the sleeve |98 toward the left along the shaft |06, as viewed in Figure 5, thereby swinging the actuating arm |84 toward the left about its pivot mounting |85 and shifting the valve actuating rod 51 outwardly (or in its raise direction) from the valve casing 54. When the shaft |06 is brought to a standstill, the springs |89 center the actuating arm |64 and thus shift the valve member 56 back to neutral position. It will be noted that when the actuating arm |84 is shifted toward the left by the speed responsive device 200, the sleeve |99 of the other device 20| is shifted along the shaft |06 by the fork but no rotation of the device 20| takes place.

Conversely, when the indicating shaft |06 rotates in a counterclockwise direction (arrow D, Figs. 5 and 6), the device 200 does not rotate with the shaft, but the overrunning clutch of the speed responsive device 20| engages to drive the latter in a counterclockwise direction with the shaft |06. The centrifugal force acting upon the fiyballs 208 causes the sleeve |99 and actuating arm |84 to be drawn toward the right, as viewed in Figure 5, thereby shifting the valve actuating rod 51 inwardly of the valve casing 54.

In order to prevent the speed responsive devices from idly rotating on the shaft |06 when they are not being driven thereby, a pair of brake bands 2|5, 2|6 are provided in contact with the sleeves 202, 203 of the devices 209, 20|, respectively. Each of the brake bands 2|5, 2|6 is trained over its respective hub or sleeve 202, 203 and one end of the brake band is suitably anchored to the housing wall 50 while the other end is connected through a spring 2|1 to the housing wall 50. The brake bands also prevent the speed responsive devices from coasting after the indicating shaft |06 has been brought to rest.

In this embodiment of my invention, the operation is generally similar to that explained in connection with the preceding embodiment. When the implement is operating at its predetermined normal speed and under the average ground conditions, the indicating shaft |06 stands stationary, but an increase in the wheel slip, or in other words, the dierence between the peripheral speed'of the tractor wheels l5, |6 and the forward motion of the tractor, will cause the shaft |06 to rotate in a clockwise direction (arrow C, Fig. 5), driving the speed responsive device 200 through its overrunning clutch and shifting the valve actuating rod 51 outwardly of the valve casing 54, causing the hydraulic cylinder 43 to raise the plow. After the section of dense soil has been passed and the wheel slippage decreases, the shaft |06 will rotate in a counterclockwise direction (arrow D, Fig. 5), thereby driving the speed responsive device 20| through its associated one-way clutch, thereby shifting the valve actuating rod 51 inwardly of the valve casing 54 to lower the plow,

lf3 'until the nor-mal: value of wheel slippage has 4been reestablished.

A third and simplified embodiment of my invention can be provided for tractors which are equipped with governors operating on the` fuel feed of the tractor to hold thetractor engine speed at a predetermined constant value any conventional manner. The governor of the tractoris indicated by the reference numeral' 220- in Figure 1v and serv-es to regulate the fuel feed so that the speed of the drive shaft |8 is substantially constant. In this case, therefore, the indication off the tractor drive shaft speed can be d-ispensed with, therebymaking it possible to eliminate the dierentia-lgear mechanism entirely, 'although the arrangement shownin Fig-- uros 1', 2, 5 and 6v can be employed byinserting a lock! bolt 22|, as shown in Figure- '7- through aligned apertures in a hub 2252-, which can be aligned with a drilledopening 2-23 through the shaft The-hub--22'2 is provided with a Harige 252-4 which is connected bybolts 22-5 to the hub 80 of the housing 86'. rlihe bevel gears |31, |3-2 should also be disengaged from each other so that the differential shaft |01- is now locked' in a stationary position, while the forward speed of the tractor over the ground is measuredfby the ground wheel |-|0 and applied through the gear |02, the pinions 94;, 95;, and the cage 93 to the ring gear |104; which drives theindicating shaft |06 always in the direction of the arrow D (Figs. 2 5; andv 6) through the pinion |05. It will now be apparent that thev indicating shaft |06 will be driven at a speed which is proportional to the speedof` the ground` wheel H0 orLin other words, the forward speed ofthe tractor. Inasmuch as the shaftv |06; will` turn in' one direction at all times (arrow D, Figs; 2, and 6), it is necessary to adjust the apparatus so that the valve elee ment 567 will be inneutral position when the tractorA is travelling forward; under load atv its normal speed. rIjhis can be accomplished by changingl the position of the fulcrum ofthe actuating arm |84 by removing the pivot holt [8 5 and inserting it throughv one of thel other aree.- tures |88 inthe lower end' of, the. annV NL41 'Br deriving the tractor, forwardly the implement can be adjusted to its desiredv operating, depth, by Shifting. the flexible member |24 of. the. wohnst` able Speed device 122i in an. axialv direetion rel,-` etive to the drive pulleys Ill, |23,-l

Durins operation, when the. plow encounters increased resistance to forward motion, the inerea'sed draitforceis oompensatedby the tractor. go. `einer 2 2 0,; which. maintains thev speed of, the

traetor drive Shaft t8: at a substantially Constant value, An, appreciable overload wilLhowever, result in an increased slip of; the tractor wheels I5; |.t,which is manifestedby. aA slowing down. ofthe tractor over the ground. This causes, the speed oit"` rotation of the indicating shaft |06' to decrease, thereby causing, the speed responsire device 2.0.1 in conjunction. with the springs,y |894 to. shift the actuatingy arm |84 to raise the plow un f1v the draft f ,orce approaches its normal value., When, the loadI is, relievedv from.. the traotontheelin. of the wheelstdecreases.; resulting in a slightly greater forward. speed of. thetractor over, thegrounm thereby turning` the indicating,4 shaft L06 ata greater speed, which shifts-theactuating avr-mt |84- to lower.' the p low. With this embodiment, when the tractor en,-

countersa slippery spotthe forward-.speed of the tractor., will, decrease due to theA increased slip; of., the, Wheeln whieh. will; errent. a, raising et, the;

'1-'4 -plow to permit the tractor to. pull the. Ilatter with decreased soil resistance.

I do not intend my invention to be limited to the particular details shown and described herein, except as set forth in the claimsv which follow. The principles of my invention may beV ap.- plied to the control of any implement propelled by a tractor, whether the implement trails be.- hind the tractor, is mounted upon the latter, or is pushed thereby.

I claim:

1. In combination with. ing traction wheel means, an agricultural imploment draft-connected tov the vehicle for travel therewith and comprising a ground workingtool shiftable within a range` of depths of ground working operation and thereby Varying the draft requirements of the tool, power actuated means for shifting said tool, means for indicatingthe forward speed of| said vehicle over the ground, means for indicating` the peripheral speedr ofsaid traction wheel means, and means comprising a differenti-al mechanism connected wi-th` said two indicating means for controlling said tool shifting means to maintain a substantially constant slippage of said traction wheel means'.

2. In combination with a draft vehicle-haviing traction wheel means, an agricultural implement draft-connected tothevehicle for travel therewith and comprising a ground workin-g tool shiftable within a range of depths of ground working operation and therebyvarying the draft requirements of the tooli, power actuated means for shifting said tool, a rst movable: -motion-transmitting device engageablewiththe ground to moveat a speed proportional tothe forward speed of the implement, a second movable motion-,transmitting devicecon-nected with said traction wheel means tomove at a speed proportionall tothe peripheral speed of the lat'- ter, a three-way gear mechanism comprising three. differentially related elements, twoof which are connected with said motion-transmitting devices, respectively, to cause the third of said elements tomove at a speed proportional tothe difference-between the forward speed or said implement and the-peripheral speed of said traction wheelmeans, and means connected with said third element for controlling said tool shifting means.

3f. In combinationing traction wheel means, an agricultura-l im plement draft-connected to the vehicle for travel therewith and comprising a ground working tool shiftable within arange of' depths of ground working operation and thereby varying the draft requirements of the tool, power actuated means for shifting said tool, afirst movable motiont-ransmitting devicel engageable withthe`V ground to-move at a speed proportional* to`v the forward speed orl the implement; asecond movable'l mo tion-tr-ansmitting` device connected4 with said' traction wheelv` means tomove ata speed proportional to the peripheral-speedof saidl traction wheel means, a three-waygearmechanism-'- comprising three differentially.- related movable el'e` ments, two. of. which are: connected withL said-I mo` tion-transmitting devices, respectively, toi cause the third. of. said elementsato-movezat-a speedlproportional; to the difference betweeni the. forward speed of saidimplementandathe peripheralispeed of said; traction wheel; means, an actuatingfmenri.- ber for controllingsaid,V tool, shifting means, a clutch engageableto connectsaid third diflfererre-` tial. element with; Said; ac tuatinamemberpz-and a draft. vehicle havwith a draft vehicle hav-- forward speed of the implement, a second movable motion-transmitting device connected with said traction wheel means to move at a speed proportional to the peripheral speed of said traction wheel means, a three-way gear mechanism comprising three diierentially related movable elements, two of which are connectedwith said motion-transmitting devices, respectively, to cause the third of said elements to move at a speed proportional to the difference between the forward speed of said implement and the peripheral speed of said traction wheel means, an actuating lever swingable through a limited range in opposite directions from a neutral position to control said tool shifting means to raise and lower said tool, respectively, a friction clutch engageable to connect asid third diierential element with said lever for swinging said lever in either direction depending on the direction of movement of said third element, said clutch being adapted to slip to accommodate movement of said third element after said lever has been swung through its range of movement, means associated with and responsive to movement of said third differential element to engage and disengage said clutch, and means for returning said lever to said neutral position upon disengagement of said clutch.

5. In combination with an agricultural implement having an adjustable ground working tool shiftable within a range of depths of ground working operation and thereby varying the speed of forward travel of said implement, power actuated means for shifting said tool, a movable motion-transmitting element the speed o movement of which is influenced by said speed of forward travel of the implement, an actuating member for controlling said tool shifting means, a clutch engageable to connect said motion-transmitting element with said actuating member, and a speed responsive device associated with and responsive to movement of said motion-transmitting element to engage and disengage said clutch.

6. In combination with an agricultural implement having an adjustable ground working tool shiftable within a range ci depths of ground working operation and thereby varying the speed of forward travel of said implement, power actuated means for shifting said tool, a movable motion transmitting element the speed of movement of which is influenced by said speed of forward travel of the implement, an actuating member for controlling said tool shifting means, said member being shiftable from a neutral position in relatively opposite directions to raise and lower said tool, respectively, said motion transmitting element being adapted to stand stationary when the tool is operating at its correct depth of ground engagement under the existing draf conditions and to move in one direction or the otherwhen the tool is operating at too great or small a depth, respectively, a clutch engageable to connect said motion-transmitting element with said actuating member to shift the latter in either direction, speed responsive means energized by movement of said motion-transmitting element to engage said clutch, and means for returning said actuating member to said neutral position upon disengagement of said clutch.

7. In combination with an agricultural implement having an adjustable ground working tool shiftable within a range of depths of ground working operation and thereby varying the speed of forward travel of said implement, power actuated means for shifting said tool, a movable motion-transmitting element the speed of movement of which is influenced by said speed of forward travel of the implement, an actuating member for controlling said tool shifting means, and a speed responsive device connected with said member and with said motion-transmitting element and responsive to changes in speedof the latter above and below a predetermined normal value for adjusting said member to shift said tool to maintain the speed of said motiontransmitting element at said normal value.

8. In combination with an agricultural implement having an adjustable ground working tool shiftable within a range of depths of ground working operation and thereby varying the speed of forward travel of said implement, power actuated means for shifting said tool, a movable motion-transmitting element the speed of movement of which is inuenced by said speed .of forward travel of the implement, an actuating member for controlling said tool shifting means, said member being shiftable from a neutral position in relatively opposite directions to raise and lower said tool, respectively, said motion-transmitting element being adapted to stand stationary when the tool is operating at its correct depth of ground engagement under the existing draft conditions and to move in one direction or the other when the tool is operating at too great or small a depth, respectively, speed responsive mechanism having a drive connection to the motion-transmitting element to be driven by said motion-transmitting element and connected with said actuating member to shift the latter in one direction or the other responsive to movement of said motion transmitting element in one direction or the other, respectively.

9. In combination with an implement movable forwardly over` the ground and having an adjustable ground-working tool shiftable withina range of depths of ground-working operation and thereby varying the speed at which said implement can travel, power-actuated means for shifting said tool, a movable element caused to move by forward travel of the implement so that the speed of movement of said element is proportional to the speed of forward travel of said implement, and means responsive to variations in the speed of movement of said element forY controlling said shifting means to selectively increase or decrease the depth of said groundworking tool according to whether the speed of movement of said element reflects respectively increase or decrease in the speed of forward travel of said implement.

l0. In combination with an implement movable forwardly over the ground and having an adjustable ground-working tool shiftable within a range of depths of ground-working operation and thereby varying the speed of forward travel of said implement, power-actuated means for shifting said tool, a movable element caused to move Y l7 ahy forward'travel `cfithezimplement that the :speed of movement :ofssaid element "ismroportional AIto the; speed fof forward 'travel pf theim- 1;plement, and `uneans :responsive :to maria-tions in :ithefspeed of movementvof saidfelement thatfre- -ground-engaging means :forpmeasuring :the forward speed 'of the vw'implement :relative to athe ground, including means actively .reflectingxvariav.tions-in fthe fforwardfspeed-.of the.implement,;and means responsive to said reiilectingxmeansafor controlling said shifting means to adjust the depth of operation o'f said ground-working tool.

12. In combination with an implement movable forwardly f over the ground :and frhaving aan 4L`adjustable ground-working tool'shiftable within a range of depths of ground-working operation to var ythe ground resistance to said tool andqhence reducing `or Aincreasing theforward speedof the limplement iby "adjusting the drag thereon, a l,ground-engaging wheel for measuring i the "for- 'Ward speed'ofthe "implement relative to the ground, a speed-responsive governor connected; to saidwheel to Vbe driven "thereby for rellecting speed-variations vin'said wheel, and power-actu- -ated- Ameanscontrolled by 'said governor..- for co'ntrolling `the sh'iftingofv said "toolfjto ho'ld `a substantially constant Aspeed 'of "forward travel. lf3. Incornbinationwith a'draft vehicle powered 'for travel over A'the "groun'dby a ground-engaging traction elementasubject toesliptrelative to the groundwin larger or smaller'famounts and thus .respectively to causedecrease Aor increase vin: the travel speed of the vehiclefaccording respectively to'increase or decrease in draft load imposd on the vehicle; an agricultural implement draftconnected to the vehicle for travel therewith and having an agricultural working part selectively adjustable to and settable in different phases of operating effectiveness and adapted, in any selected phase, to encounter agricultural conditions of varying magnitude imposing varying resistances to travel of said part with the vehicle and accordingly imposing varying draft loads on the vehicle such as to affect the ratio of vehicle travel speed to slip of the traction element relative to the ground; power actuated means connected to the working part and controllable to adjust and set the working part in different phases of operating electiveness; means associated with the vehicle for reecting variations in the ratio of vehicle travel speed to slip of the traction element relative to the ground; and means connected between said ratio-reflecting means and the power actuated means for controlling said power actuated means to respectively decrease and increase the operating effectiveness of the working part according to decrease and increase in the ratio of vehicle travel speed to slip of the traction element relative to the` ground.

14. For an agricultural unit including a draft vehicle powered for travel over the ground by a ground-engaging traction element subject to slip relative to the ground in larger or smaller amounts and thus respectively to cause decrease :traveltherewith and-havingiangagriculturalswork- -ingz'part selectively aad-instable :to ,and settalolerfin dii'eernt `phases :of fdperating effectiveness Aand adapted in any selected phase to encounter'agrii-:cultural conditions-tof varying-magnitude; impos- `fing vvaryingrresistafnces t,o;travel ofssaidziartwith .the vehicle and accordingly imposing varymg *a draft flea-ds on Vthe'v vehiclegsuch :ras :to g-aiect zthe :'ratio'- of Avehicle travel fspeed: to slip 'sofi-the traction :element relativettoltheqgroundnand powergactu- .,atedlffmeansfconnccted .to thefworkinggpart :and .controllable lto :adjust ,and s et :thecworking part :different phases cf operating eiecltiv encss,zthe impro vement comprising :means connectibleswith the ,vehicle for 'reflecting variations in :theratio of l.vehicle :travelcspeed ato :slip of lthe traction `element :relative to thergrcund; fand :means sconnectibl-e rbetween fsaid :ratio-reiecting; means and the ,power actuated means for :control-ling :jpower actuated 'means to respectively .decrease andfgincrease :the operating @effectiveness of :the working part V.according .to .decreaseiand .increase .ii-n 4the :ratio :of vehicle :travel:speeditcsslipnofathe i' .traction Velement :relativeftogthe ground.

l5. combination with;aidraftivehiclepowered n: for travel f overf `the groundfby=a :ground-engaging traction elemen'trand subject'rfto decrease @or iinvcrease inthe .travel speed :according 4respectively to 'increase or decrease iin draft -load imposed-'lon the vehicle; van fag-ricultural implement-draftconnected Vto thevehicle-:fori-traveltherewith--and :'having an agricultural work-ing -pa-rt f selectively adjustable to and settable in different phases 'of operating -effectivenesseand adapted, in-any-selected phase, to encounter agricultura-1 conditions of varying -magnitude imposing varying rels'istances 1vtotrav'el-of said partfwith-the vehicle .and accordingly imposing-'varying `draft'loads ion -the Lvehicle isucheasfto affect th-e `travel-speed of the vehicle; power actuated means connected to the working part and controllable to adjust and set the working part in different phases of operating eifectiveness; means associated with the vehicle for reflecting variations in the travel speed of the vehicle; and means connected between said reflecting means and the power actuated means for controlling said power actuated means to respectively decrease and increase the operating effectiveness of the working part according to decrease and increase in the Vehicle travel speed.

16. For an agricultural unit including a draft vehicle powered for travel over the ground by a ground-engaging traction element and subject to decrease or increase in the travel speed according respectively to increase or decrease in draft load imposed on the vehicle, an agricultural implement draft-connected to the vehicle for travel therewith and having an agricultural working part selectively adjustable to and settable in different phases of operating eiectiveness and adapted in any selected phase to encounter agricultural conditions of varying magnitude imposing varying resistances to travel of said part with the vehicle and accordingly imposing varying draft loads on the vehicle such as to aiect the travel speed of the vehicle, and power actuated means connected to the working part and controllable to adjust and set the working part in different phases of operating effectiveness, the improvement comprising: means connectible with the vehicle for reflecting variations in the travel speed of the vehicle; and means connectible between said reflecting means and the power actuated means for controlling said power actuated means to respectively decrease and increase the operating effectiveness of the working part according to decrease and increase in the vehicle travel speed.

17. For an agricultural unit including a draft vehicle having traction means provided with a rotary part, an agricultural implement draftconnected to the vehicle for travel therewith and having a ground-working tool shiftable within a range of depths of ground-working operation and thereby varying the draft requirements of the tool, and power actuated means for shifting the tool, the improvement comprising: a first movable motion-transmitting device connectible to the unit for movement ata speed proportional to the forward speed of the unit; a second movable motion-transmitting device connectible to the aforesaid rotary part to move at a speed proportional to the peripheral speed of the traction element; a. three-way gear mechanism including three differentially related movable elements, two of which are connected respectively with said motion-transmitting devices to cause the third of said elements to move at a speed proportional to the diierence between the forward speed of the unit andthe peripheral speed of the traction element, an actuating member for controlling said tool shifting means; a clutch engageable to connect said third differential element with said actuating member; and means associated with and responsive to movement of said third differential element to engage and disengage said n clutch.

shift said actuating member in relatively opposite directions, respectively; and the drive connection of the speed responsive mechanism to the motion-transmitting element includes a pair of opposed one-way clutch devices drivingly connecting said speed responsive devices with said motion-transmitting element and providing for transmitting motion from said motion-transmitting element to said speed responsive devices, selectively, by movement of said motion-transmitting element in relatively opposite directions, respectively.

19. The combination set forth in claim 18, including the further provision 0f a pair of braking means, one for each of said speed responsive devices, for respectively holding one of the devices stationary while the other is being driven by said motion-transmitting element, and opposed biasing means connected with said actuating member for returning the latter to said neutral position when said motion-transmitting element stops moving,

THOMAS W. B'OHMKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 718,221 Schmitthenner Jan. 13, 1903 739,386 Cady Sept. 22, 1903 841,318 Foster Jan. 15, 1907 886,910 Williams et al. May 5, 1908 1,931,815 Conley Oct. 24, 1933 2,016,626 Constantinesco Oct. 8, 1935 2,356,231 Ferguson Aug. 22, 1944 2,363,292 Brown Nov. 21, 1944 2,394,210 Sherman Feb. 5, 1946 2,405,334 Silver Aug. 6, 1946 2,423,057 Thomas et al June 24, 1947 2,430,696 Acton Nov. 11, 1947 FOREIGN PATENTS Number Country Date 541,436 Great Britain Nov. 26, 1941 42,266 Switzerland Dec. 24, 1907 

